We are investigating the physiological and biochemical mechanisms of intestinal transport stimulation using two experimental models: (a) the diabetic rat, and (b) the vitamin D repleted rat. The intestinal transport techniques used with these two models are 1) in vivo luminal perfusion of the in situ intestine, 2) everted intestinal sacs, 3) isolated villi, and 4) isolated intestinal epithelial cells. Transport of the following substances is being studied: hexoses, neutral amino acids, and electrolytes, in particular, calcium. Concentrations of transported substances are being measured in the intestinal lumen, mucosal cells, underlying intestinal tissues, and plasma. Biochemical studies of transport stimulation deal primarily with protein synthesis. Labeled amino acids are incorporated into protein by isolated epithelial cells from control and transport stimulated rats. The proteins are separated by electrophoresis on acrylamide gel, to seek specific proteins related to transport stimulation.